1. Field of the Invention
This present invention relates generally to wireless communication systems, and more particularly to wireless communication systems utilizing Orthogonal Frequency Division Multiplexing (OFDM) techniques.
2. Description of the Related Art
In conventional telephone systems, voice communication between users is realized using a dedicated physical channel in a “circuit-switched” network. In wireless communication systems, such as analog cellular telephone systems, voice communication is similarly realized with the use of a dedicated frequency channel, for example, with the use of Frequency Division Duplex (FDD) communications. In digital cellular telephone systems, voice communication is similarly realized using a dedicated time slot channel, for example, with the use of Time Division Duplex (TDD) communications.
Movement over the past several years, however, has been in the direction of “packet-switched” communications. Packet-switched communications involve small data packets which carry data and are addressed to particular recipients. The physical channel over which the data packets are sent is shared between multiple users, and therefore multiple data packets from multiple users may adversely affect (i.e., slow down) the transmission of data packets. Packet-switched communications have become popular due to the popularity of the Internet. Wireless communication systems, such as cellular and personal communication systems (PCS), have begun to embrace packet-switched communications so that high speed data, such as data available over the Internet, may be obtained. Even for communications involving voice, packet-switched methods have been advocated with use of, for example, Voice Over IP (VoIP).
Wireless communications systems in particular operate over limited spectral bandwidths. These systems must make highly efficient use of the scarce bandwidth resource to provide good service to a large population of users. Good services require that the system have sufficient capacity and be highly responsive to its user requests. Accordingly, what is needed is a wireless communication system that is spectrally efficient and responsive in communications involving voice and/or high speed data.